Overvoltage protector



July 17, 1951 R. 1.. BROWN OVERVOLTAGE PROTECTOR 4 Sheets-Sheet 1 Filed Oct. 15, 1947 llllll INVENTOR HUBER T LUlL/ELL BRUZUN ATTORNEY July 17, 1951 ow 2,560,628

OVERVOLTAGE PROTECTOR Filed Oct. 15, 1947 4 Sheets-Sheet 2 lNVENTOR HUBERT LU/l/ LL BHUlL/N M ATTORNEY July 17, 1951 R. 1.. BROWN 2,560,628

OVERVOLTAGE PROTECTOR Filed Oct. 15, 1947 4 Sheets-Sheet 5 .jirmyuuum INVENTOR HUBERT LUlz/E L BHUlz/N ATTORNEY July 17,1951 R. L. BROWN OVERVOLTAGE PROTECTOR 4 Sheets-Sheet 4 Filed Oct. 15, 1947 HUBER LUZL/ELL ATTORNEY Patented July 17, 1951 OVERVOLTAGE PROTECTOR Robert L. Brown, Teaneck, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. J., a

corporation of Delaware Application October 15, 1947, Serial No. 779,992 3 Claims. (Cl. 200-106) The present invention relates to an overvoltage protector for electrical enerator systems and more particularly to improvements in the system and protector of the type shown in the copending application for U. S. patent Serial No. 701,322, filed October 4, 1946, by Robert Lowell Brown, now U. S. Patent No. 2,522,601.

An object of the invention is to provide an improved relay operated latch mechanism in which an electromagnet acts upon an armature movable separate from the latch so as to release the latch only after the armature has approached quite close to the electromagnet to cause a spring biased plunger or rod to actuate a plurality of switches.

Another object of the invention is to so arrange the plunger that it may be manually operated to reset the latch and switch mechanisms.

Another object of the invention is to provide an overvoltage protector which does not respond to sudden surges of short duration of over voltage.

It is desirable in the event of an overvoltage on one generator of a parallel arrangement that the other protectors do not trip due to surges caused by the finite time of operation of the faulted protector, reverse current relays, regulators and line switches. While the regulators of the normally functioning generators will automatically tend to keep the non-faulted protectors from tripping after a short, an object of the invention is to provide means for efiecting an immediately acting time delay (of short duration) to keep the protectors from tripping before the regulators can take over.

Another object of the invention is to provide an immediately acting time delay (of short duration) for the protectors which is introduced by the use of short circuiting slugs (rings) of copper arranged concentric with the coil on the electromagnet. Thus with the time delay in the protectors plus the correcting action of the regulators the non-faulted protectors will not trip when a parallel system is disturbed by an overvoltage generator.

Another object of the invention is to provide a vacuum sealed container for the protector mechanism, including a bellows through which the reset plunger may be manually actuated to reset the latch and switch mechanism.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example.

In the drawings:

Figure 1 is a perspective view of the overvoltage protector showing the vacuumtight casing and manually operable reset bellows:

Figure 2 is a perspective view of the overvoltage protector with the casing removed.

Figure 3 is an enlarged sectional view of the overvoltage protector with the latch shown in the released position.

Figure 4 is a fragmentary end view of the switch mechanism showing the armature and latch mechanism.

Figure 5 is an end view of Figure 3 taken along the lines 5-5 and looking in the direction of the arrows.

Figure 6 is a diagrammatic view showing the overvoltage protector connected into a generator system.

Referring to the drawings of Figures 2-3 there is shown the overvoltage protector which includes an electromagnetic coil l0 supported by a bracket II which with a second bracket l2 are fastened to a supporting plate l3 and base member or panel MA by bolts H.

The electromagnetic coil III has an armature l5 pivoted on an edge l6 formed at the outer end of the bracket II. A third bracket arm I! is fastened to the bracket H by a bolt H; which also fastens thereto a member IS. A spring 20 is connected at the free end of the member I9, while the opposite end of the spring 20 is connected to the upper end of the armature l5 so as to bias the armature l5 about the edge I6 in a clockwise direction.

Positioned adjacent the armature I5 is a latch member 2| pivotally supported at one end by a spring arm 22. The latch member 2| is arranged to engage a shoulder portion 23 of a reset plunger or push rod 24. The push rod 24 is slidably mounted in portions 25 and 26 of the bracket 12.

At the upper end of the push rod 24 there is provided a head portion 21. Positioned between the head portion 21 and the bracket portion 25 is a coil spring 28 which biases the push rod 24 upwardly. A stop 29 is provided at the lower end of the push rod 24 to engage the bracket portion 26 so as to thereby limit the upward movement of the push rod 24 under the biasing force of the spring 28. A cup shaped depression 30 is formed in the supporting plate I3 for receiving the lower end-of the push rod 24 when in the depressed position.

The supporting plate 13 has an upstanding flanged portion 3| extending about the outer edge thereof to which there is sealingly connected the lower edge of casing 32 which encloses the protector mechanism.

The casing 32 has an opening 33 formed therein through which projects the head portion 21 of the push rod 24. A bellows 34 surrounds the head portion 21 and the opening 33 and is sealingly connected to the casing 32. The upper end of the head portion 21 is operably connected interiorly to the bellows 34 so that depression of theJoellows 34 effects downward adjustment of the push rod 24 so as to effect engagement of the shoulder 23 by the latch member 2|.

The armature l carries a headed stud 35, the shank of which extends loosely through an aperture in the latch member 2|, thus forming a loose or lost motion connection between the armature l5 and latch member 2|. With this arrangement it will be seen that upon energization of the electromagnet Hi the voltage at which the armature I5 starts to move is determined by the spring 20. After the armature l5 has approached quite close to the pole face of the electromagnet ID (at which position the pull of the electromagnet I0 is much greater) the head of the stud 35 engages the latch member 2| and pulls it oil the step 23 of the push rod 24, thus permitting the rod 24 to move upward under the biasing force of the spring 28, to

operate a plurality of switch contacts, aswill be explained.

Mounted on the bracket arm I! by bolts 36 is a switch assembly comprising insulating spacers 31, 38, 39,- 40, 4|, 42 and 43 and contact carrying spring arms 44, 45, 46 and 41 suitably insulated by the spacers.

As shown in Figure 5 there is further mounted on the bracket arm I! by bolts 36A 8. second switch assembly comprising insulating spacers 31A, 38A, 39A, MA, MA, 42A and 43A and contact carrying spring arms 44A, 45A, 46A and 41A insulated by the spacers.

Also secured to the bracket arm H by the bolts 36 and 36A are insulation strips 50 and 5|. Contact carrying spring arms 52 and 53 are fastened respectively to the insulation strips 50 and 5| at a point intermediate the two switch assemblies 36 and 36A.

Also secured to the insulation strip 50 and at the opposite side thereof from the spring arm 52 is a spring strip 54 which is connected to the contact strip 52 at the contact button 55. The contact button 55 is arranged to cooperate with a contact 56 carried by contact spring strip 53.

As shown in Figure 4, there are positioned at opposite sides of the contacts 55 and 56 permanent magnets 51 and 58 held in a bracket 59 aifixed at the upper end of the bracket arm The bracket arm ll thus closes a magnetic circuit between the permanent magnets 51 and 58 r at the lower end thereof while at the upper end a magnetic flux flows across the contacts 55 and 5G tending to blow the arc resulting upon opening the contacts outward toward the left as viewed in Figure 3.

The spring arms "-45, 44A-45A; 46-41, and 46A-41A likewise cooperate respectively in open- .ing' and closing several circuits as will be ex- Afllxed to the spring arm 54 is a U-shaped member 55 operably connected to spring contact arm 44 and A by insulated connectors 65, while the arms 44 and 44A are similarly connected to spring contact arm 45 and 46A respectively by insulated. connectors 61.

It will be seen then that upon downward movement of the push rod 24 to a latched position the main switch contacts 55 and 55 will be closed as will the spring switch arms 4445, 44A45A,

46-4'|, and EA-41A. However upon the electromagnet l0 becoming energized and drawing the armature I5 toward it in a counter-clockwise direction the stud 35 will draw the latch member 2| from the step 23, so as to release push rod 24. The upward movement of the rod 24 under the biasing force of the spring 28 will then cause switch arm 52 to open contacts 55-56 and switch arms 44, 44A, 46 and 48A to open their respective contacts.

In order to compensate for changes in the resistance of the electromagnet l0 due to variations in temperature there is provided a resistance 10 having a small temperature coefficient of resistance, preferably wound of Nichrome wire. The resistor 10 is mounted on the supporting member l3 and is connected in series with the electromagnetic winding ill, the resistance of which is relatively small compared to that of the resistance I0 so that any change in the relative resistance of winding I0 due to temperature effects the total resistance by a negligible amount.

Moreover in order to introduce an immediately acting time delay (of short duration) in the response of the electromagnetic winding It to change in an energizing current, there are provided short circuited copper rings II which are arranged concentric with the winding of the electromagnet Ill. The copper rings 1| tend during change in the energizing current of the electromagnet I!) to generate a magnetic flux retarding the build up of a sufl'icient magnetic. flux by the electromagnet ID to actuate the armature I5, thus providing sufiicient time lag to prevent tripping of the latch 2| by surge voltages.

The electromagnet l0 and the several switch contacts. controlled thereby are connected by conductors 12 leading through a suitable insulation cement 13 provided in the base of-the supporting member l3, as shown in Figure 5 The conductors 12 are in turn connected by conductors to suitable external terminals 14 mounted in the base member |3A, as shown in Operation The purpose of the overvoltage protector device heretofore described, is to prevent damage to an airplanes electrical equipment when malfunc tioning of a generating system causes excessively high voltage. The protector device is arranged to open the field circuit of the malfunctioning generator and in addition to effect the disconnection of its control equipment from the generator and to disconnect the generator from the main line without affecting other generating systems connected in parallel to the line. Each of said generating systems are provided with a like protector device.

A typical system in which the protector device 32 may be used is illustrated in Figure 6 and may include a generator having a field winding 8| and an interpole compensatin winding 82. Output line 83 of the generator 80 is grounded, while output line 84 may be connected to a main bus line 85 through a line switch 86 operated by a solenoid 81.

The control equipment for the generator is indicated generally by the numeral 90 and may be oi a type described and claimed in the copending application Serial No. 621,515, filed October 10, 1945 by William R. Holmes.

The control equipment 90 includes a variable resistance carbon pile 9i connected in series with the generator field 8i through a conductor 92. The field 8I is connected through conductor 93 to output line 83 and the opposite end of the carbon pile 9| may be connected to the output line 84 through a conductor 94 and the main switch contacts 55 and 56 of the protector device 32.

The variable resistance carbon 'pile 9I may be controlled by an adjustable armature 95 shown schematically in Figure 6 and which may be of a type described and claimed in U. S. Patent No. 2,427,805, granted September 23, 1947, in the name of William G. Neild and assigned to Bendix Aviation Corporation.

The armature 95 may be controlled by an electromagnetic winding 98 which may be connected across the generator output lines 83 and 84 by grounded conductor 91 and conductor 98. The conductor 98 may be connected to line 84 through switch members 44-45 of the protector device 32. I

Connected across the interpole compensating winding 82 by a conductor 99 and grounded conductor 99A is a potentiometer I having a center tap I 00A connected to a compensating winding IIII for affecting the carbon pile 9| so as to maintain a predetermined division of load between the several parallel connected generators as is explained in the aforenoted copending application Serial No. 621,515.

The opposite end of the compensating winding IOI may be connected to an equalizer line I02 through a conductor I03, relay switch I 04, and switch members 44A and 45A of the protector device 32. The relay switch I04 is controlled by an electromagnetic windin I05 connected across the output lines 83-84 by grounded conductor I06 including resistance I06A, conductor 98 and switch contacts 44 and 45 of protector 32.

The relay winding I05 is controlled by a pilot switch I01 biased by spring tension to the position shown so as to close switch contact I08. Switch I01 is connected to conductor 98 while contact I08 is connected to conductor I06 so that upon switch I01 closing contact I08, relay winding I05 is shunted out of operation.

The pilot switch I 01 is controlled by an electromagnetic winding I09 connected through conductor 98 and switch contacts "-45 of the protector device to output line 84 and through grounded conductor IIO to output line 83.

Upon the output generator voltage rising above a predetermined value the relay switch arm I01 is biased by relay I09 so as to open contact I08 and close a contact III. The latter action opens the shunt circuit of relay winding I05 causing the winding I05 to close switch I04 whereupon the compensating winding IN is connected into operation and to the equalizer line I02.

Moreover upon relay switch I01 closing contact I I I a current winding I I2 is connected across the open line switch 86 by a conductive passage leading from line 84 through switch contacts 44,-45 of the protective device 32, conductor 98, switch I81, contact III, current winding H2, and a con ductor II3 to the main bus line 85. The winding H2 is wound about a permanent magnet H4 and is arranged to cooperate therewith so that upon a current flow from the generator 80 to the main bus line the magnetic effect of coil I I2 and permanent magnet II4 will exert an additive effect biasing a relay switch II5 to close contact H6.

The relay switch H5 is connected by a conductor II1 to conductor 94 and through switch contacts 55 and 56 to the output line 84. The contact H6 is connected by conductor II 8 through the switch contacts 48-41 of the protector device 32 to the line relay 81. The closing of switch II5 will then cause energization of the line relay 81 and the closing of the line switch 88 which will shunt differential current winding I I2 out of operation.

Cooperating with the winding H2 is a second current winding I20 connected across the interpole compensating winding 82 through conductor I2I and grounded conductor I22. So long as the current flow is from the generator 80 to the main line 85 the winding I20 will exert an additive effect with the permanent magnet II4 tending to hold the control switch II5 closed. However in the event the output of the generator 80 decreases to such a point that the current output of the generator is below that of the main bus line 85, then the winding I20 will exert a differential effect with the permanent magnet I I4 tending to decrease the magnetic effect acting on the relay switch II5 so that the switch II5 under spring force is biased to a position opening contact H6. The latter action deenergizes the winding 81 causing line switch 86 to open.

As shown schematically in Figure 6 and specifically in Figures 2-'-5 switch contacts 46-41, 44-45, 55-56, 44A-45A, and 46A-41A may be closed by manually actuating the push rod 24. The same may be latchedin the latter position through action of the latch mechanism 2I as heretofore explained.

The closing of switch contacts 46A-41A connects a sensing coil, the electromagnetic winding I0, across the field 8| of the generator 80 through conductors I30 and I3I.

When the voltage across the field 8! reaches a predetermined excessive value for any reason, the sensing coil I0 actuates the armature I5 and through the studs 35 the latch 2I, thus releasing the reset rod 24 and opening the main contacts 55-56, and the four pairs of auxiliary contacts 46-41, 44-45, 44A-45A, and 46A-41A.

In the latter event the following action takes efiect. The contacts 46-41 open the potential circuit for the line relay 81 and thereby cause line switch 88 to open and effect deenergization of current winding I20. The contacts 44-45 open the potential circuits for the carbon pile voltage coil 96, relay voltage coil I05, and relay voltage coil I09. Deenergization of coil I09 causes in turn relay switch I01 to open contact III and thereby the circuit to differential current coil H2. The main contacts 55-50 open the generator field circuit. The auxiliary contacts 44A and 45A open the circuit of the compensating winding IN. The auxiliary contacts 46A and 41A open the circuit of the sensing coil I0.

As an alternative arrangement the switch 44A-45A may be normally open so that upon the latch 2I releasing the reset rod 24 the switch 44A-45A may close a circuit to energize a warning device such as an electric light or bell to in- .indicated herein as 32A, 32B and 32C, respectively.

Surge voltages due for example to a faulted generator will not actuate the overvoltage protector of the other non-faulted generators. This condition is achieved by the incorporation of the copper washers H, which act as shorted turns on the sensing coil I0. Such shorted turns in an inductive system generate flux that opposes the flux generated by the coil Ill. Thus during change in the energizin current of the coil Ill this opposition retards the build-up of suiiicient coil flux to actuate the armature I5, so as to provide a sufficient time lag to prevent tripping of the latch 2| by surge voltages. This time lag is further insured by the construction of, the armature l5 and latch 2|. The armature has studs arranged to trip the latch 2| after the armature has traveled about two-thirds of its distance to the electromagnet ID. This construction also permits the tripping voltage to be unafiected by friction.

Once the overvoltage protector has operated the reset rod 24 may be pushed down to reset the mechanism by manually compressing the bellows 34.

The overvoltage protector is sealed within the casing 32 so as to protect the same from moisture, dirt and atmosphere.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangements of the parts may be made to suit requirements.

What is claimed is:

1. An overvoltage protective device, comprising, in combination, a supporting plate, a first bracket projecting from the supporting-plate. an electromagnetic coil fastened to the first bracket, a second bracket secured to the first bracket, a switch assembly supported by the second bracket, said first bracket extending along said electromagnet coil and having a knife-like edge at a free end thereof, an armature pivotally mounted on said edge and cooperating with the electromagnetic coil, a spring biasing said armature in opposition to the magnetic force of said coil, a spring arm fastened to said first bracket, a latch member pivotally supported by the spring arm and having an aperture therein, a stud projecting from the armature through said aperture and providing a lost motion connection between said armature and latch member, a third bracket fastened to said supporting plate, a rod slidably supported by said third bracket and having a shoulder portion engageable by said latch member, a control arm operatively connecting said rod to said switch assembly, a spring operatively positioned between said third bracket and rod for biasing said rod in one direction, and a manually operable means for actuating said rod into latching engagement with said latch member in opposition to said last mentioned spring.

2. An overvoltage protective device, comprising, in combination, a supporting plate, a first bracket projecting from the supporting plate, an electromagnetic coil fastened to the first bracket, a second bracket secured .to the first bracket, a switch assembly supported by the second bracket, said first bracket extendin along said electromagnet coil and having a knife-like edge at a free end thereof, latching means including an armature pivotally mounted on said edge and cooperating with the electromagnetic coil, a spring biasing said armature in opposition to the magnetic force of said coil, a third bracket fastened to said supporting plate, a rod slidably supported by said third bracket and having a shoulder portion engageable by said latching means, a control arm operatively connecting aid rod to said switch assembly, spring means for biasing said rod in one direction, and manually operable means for actuating said rod intolatching engagement with said latching means, in opposition to said last men-- tioned spring means.

3. The combination defined by claim 2 including a first switch contact carried by the control arm, a second switch contact carried by the switch assembly, said first switch contact positioned in contactin relation with said second switch contact upon movement of the rod into the latching position, and said first switch contact biased but of contacting relation with said second switch contact upon the rod being released from said latching position and actuated under the biasing force of the spring means.

ROBERT L. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

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